Auto-injector

ABSTRACT

A device for auto-injection of a dose of medicament, comprises a housing arranged to contain a medicament container therein and a contact part intended to be applied against an injection site, a needle cover surrounding a needle arranged to the medicament container and extending at least the length of the needle, spring elements for, upon activation, pushing the needle past the end of the cover as well as operating the medicament container to supply the dose of medicament, first locking elements for locking the spring elements in a pressurized state, first activating elements for, upon manual operation, releasing the spring elements for injection. There is a second locking element capable of locking the first activating element and a second activating element, capable of releasing the second locking element when the contact part is exposed to pressure.

TECHNICAL FIELD

The present invention relates to an auto-injection device intended forinjection of a dose of medicament, comprising a housing arranged tocontain a syringe therein and comprising a contact part intended to beapplied against an injection site, a needle cover surrounding the needleof the syringe, spring means capable of, upon activation, pushing theneedle through the needle cover as well as injecting the dose ofmedicament, first locking means capable of locking said spring means ina pressurised state, and first activating means capable of, upon manualoperation, releasing said spring means for injection.

BACKGROUND OF THE INVENTION

Automatically, or semi-automatically activated, injection devices havebeen on the market for many years. One of the first types was intendedfor war-times, which type was activated by merely pressing or slammingthe injector against a body part thereby activating it. The main concernwas to have the medicament injected as fast as possible, without muchconcern for the patient or for safety aspects such as unintentionalfiring.

Since auto-injectors began to be used by “normal” patients, such as forexample asthmatics, and also since the AIDS risk has become an importantissue, the handling and safety aspects have become much more important.Patent document U.S. Pat. No. 5,085,642 discloses an auto-injectorcomprising a preloaded compression spring acting on a plunger, which inturn acts on a syringe. Before use the needle is protected inside theinjector from being contaminated. In order to activate the injector acap has to be removed so that a firing button may be available. When thefiring button is depressed, the plunger is released, whereby it pushesthe needle out of the cover and the medicament is discharged with thehelp of the compression spring.

With the auto-injector according to U.S. Pat. No. 5,085,642, once thecap has been removed, there is a pronounced risk of unintentionalmisfiring if the patient depresses the firing button before the injectoris placed against the intended injection location. This may be fatal ifthe patient for example suffers from an acute allergic attack andrequires an injection immediately in order to seize the attack. Further,with this injector, the needle is completely exposed after theinjection, whereby there is a pronounced risk of being pierced orscraped by the needle.

Patent document U.S. Pat. No. 5,681,291 discloses an auto-injectorcomprising a first and a second device for performing the injection. Thefirst device retracts a needle cover surrounding the needle before useinto the injector housing when a predetermined force is placed on theinjector, thereby exposing the needle so that it can be pushed into thepatient. When the needle cover has been retracted a certain distance,the second device is activated, which acts on the plunger of the syringefor injecting the medicament. The injector may also be provided with aspring for extracting the needle cover from the housing once theinjector is withdrawn from the injection site, thereby covering theneedle after use. The needle cover may also be locked in that extractedposition.

One drawback with the injector according to U.S. Pat. No. 5,681,291 isthat the injector has to be pressed actively by the patient with arather high force in order to overcome the holding force of the needlecover and for entering the needle into the body of the patient. Thisforce is even more pronounced when an extracting spring is used. This inconnection with necessary step of pulling free a flexible arm on theoutside of the injector in order to activate it makes the handling ofthe device very cumbersome and not user-friendly nor easy to use. Thepatient needs to be very active and to perform a certain number ofactions, some with considerable force, in order to inject themedicament. In a crisis situation, such as described above, there may bea risk that the patient fails to handle the injector properly. Theinjector is also not suitable for children because of this.

Another aspect with the injector according to U.S. Pat. No. 5,681,291 isthat the needle cannot be kept from becoming contaminated since theneedle cover has an opening in the injection direction. The needle mayof course have a removable cover or sheath, but removal of that wouldconstitute yet a step in order to activate the injector.

BRIEF DESCRIPTION OF THE INVENTION

The aim of the present invention is to provide an auto-injection devicewithout the above mentioned drawbacks which is user-friendly, easy touse, with a high degree of safety and greatly reduces the risk ofunintentional misfiring.

This aim is accomplished according to the present invention with aninjection device according to claim 1. Further particular features ofthe present invention are apparent from the dependent claims.

With an auto-injection device according to the present invention severaladvantages are obtained. The main activating means, which releases thespring means that performs the ejection of the needle and the injectionof the medicament can not be operated unless the injector is actuallypressed against the injection site. It is thus required to perform a“two-step” operation in order to inject the medicament. First theinjector is pressed against the injection site, whereby the locking ofthe activator or firing button is released. After that the button may bepressed whereby the spring-loaded syringe is activated and themedicament is injected. This reduces the risk that the injector ismisfired before it is placed on the appropriate and desired locationbecause the activator cannot be depressed unless there is a pressure onthe contact part of the injector.

The design is also so that if the injector is lifted again afterpressing it against the injection site, if for example the patientwishes to use another site, the activator is again locked, i e theactivator is always locked when the contact part of the injector is notunder pressure. Further, the “two-step” operation can not be done in theopposite way, i e by first pressing the activator and then pressing theinjector against the injection site, thereby further preventingaccidental misfiring of the injector. Even so the injector according tothe invention is simple to use and user-friendly. There is no need forremoving safety caps or bending away safety pins in order to activatethe injector, the patient just have to press the injector against thedesired injection location.

In a preferred embodiment of the invention, the contact part is theneedle cover, which completely covers the needle before use. Uponinjection, the needle penetrates the needle cover. This enables theneedle to be kept sterile before use. There is thus no need for removalof such covers before injection. When the injection cycle is almostcompleted, the spring-loaded needle cover is released from the housingso that it can be pushed out around the needle upon withdrawal of theinjector from the injection site. The needle of the injector of thepresent invention is thus never exposed or visible to the patient, whichenhances the safety of the device and also provides a comfort aspect topatients that do not like to see needles, such as children. When thecover is pushed out, it is locked in that position, thereby preventingthe needle to becoming exposed by pushing the needle cover back into theinjector.

These and other aspects of, and advantages with, the present inventionwill become apparent from the following detailed description of theinvention and from the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed description, reference will be made to theaccompanying drawing where

FIG. 1 is a cross-sectional view of the rear part of the auto-injectoraccording to the invention,

FIG. 2 is a cross-sectional view of the front part of the auto-injectoraccording to FIG. 1,

FIG. 3 is an exploded view of the housing part of the auto-injectoraccording to FIG. 1,

FIG. 4 is an exploded view of the injection mechanism of theauto-injector,

FIG. 5 is an exploded view of the force actuating means of theauto-injector,

FIG. 6 shows the first step of activating the auto-injector of FIG. 1,

FIG. 7 shows the second step of activating the auto-injector,

FIG. 8 shows the penetration of the needle of the auto-injector,

FIG. 9 shows the activation of a needle cover comprised in theauto-injector, and

FIG. 10 shows a variant of a holding means for a syringe arranged in theauto-injector.

DETAILED DESCRIPTION OF THE INVENTION

The injector according to a conceivable embodiment shown in the FIGS.1-9 comprises an elongated generally tubular central housing 10 open atboth ends. The central housing is provided with openings 11. One end ofthe housing is arranged with a front end piece 13 with a somewhatconical shape. The other end of the central housing is arranged with anend cap 12 attached to the housing. The end cap is provided with atubular passage 14. The inner end of the tubular passage is arrangedwith conical surfaces 16. A tubular body 18, hereafter named needlecover, is slidably arranged in the front end piece and protruding ashort distance from the end of the front end piece.

The end of the needle cover protruding from the front end piece isarranged with a closing end wall 20. Behind the needle cover, a tubularbody 21, hereafter named front extension tube, is slidably arranged inthe housing, where its front end is abutting the rear end of the needlecover. The front extension tube 21 is further provided with elongatedslots 22 extending from the front end. A syringe 24 is arranged insidethe needle cover with its needle 26 pointing at the end wall. That areaof the end wall is preferably arranged thinner than the rest of theneedle cover. The diameter of the syringe corresponds substantially tothe inner diameter of the needle cover. The inner end of the syringe isprovided with transversally arranged protrusions 28 adapted to fit intothe elongated slots of the needle cover. A seal 30 is provided betweenthe inside of the needle cover and the syringe and a circumferentialledge on the syringe body, thereby providing a closed sealed off space34 for the needle.

The inner end of the front extension tube 21 is further provided with acircumferential outwardly directed ledge 36, which ledge is providedwith a ring 38, where the inner diameter of the ring corresponds to theouter diameter of the ledge. A lock ring 40 is arranged abutting theledge of the needle cover and provided with a number of legs 42protruding backwards, to the left of FIG. 1, and somewhat outwards. Theends of the legs are provided with inwardly directed protrusions 44.

A tubular body 46, hereafter named rear extension tube, is arrangedinside the rear part of the needle cover and extending some distancebackwards, to the left of FIG. 1, from the needle cover. The rearextension tube is detachably connected to the front extension tube 21via snap fits 32 on the front extension tube in recesses 47 on thesurface of the rear extension tube. The rear part of the rear extensiontube is arranged with a number of elongated slots 48, where some extendall the way to the end of the tube while some are left with some land50. Inside the rear extension tube, an activator 52 is arranged. Itcomprises a generally tubular body 54 where one end protrudes throughthe passage of the end cap, forming an activation button. The activatoris further provided with a number of protrusions 56 arranged around thecircumference. The protrusions abut the end of the tubular passage withside surfaces. The opposite side surfaces of the protrusions arearranged somewhat conical inwardly. The other end of the activator isprovided with a number of elongated slots, thereby forming a number ofarms 58. The ends of he arms are arranged with outwardly directedprojections 60, abutting the inner wall of the rear extension tube. Theinner surface of the activator is generally cylindrical apart for asection near the inner end, to the right of FIG. 1, which is providedwith a conically narrowing surface 62.

A locking mechanism 64 is further provided between the housing and theactivator. It comprises a circular body 66 attached between the end capand the housing. A number of arms 68 are arranged on the body, where thearms are protruding inwards and backwards as seen in FIG. 1. The ends ofthe arms are arranged with inwardly directed protrusions 70 which extendthrough those slots of the rear extension tube provided with land,whereby the backward facing surfaces of the protrusions abut against theconical surface of the ring of the activator. Preferably these surfacesare provided with the corresponding conicity. The arms are furtherprovided with sidewardly extending protrusions 72, which rest againstthe outer surfaces of the rear extension tube adjacent the slots. Acompression spring 74 is arranged between the locking mechanism 66 andthe ledge of the front extension tube 21. Inside the activator, aplunger 76 is arranged, which plunger extends to, and abuts the plungerof the syringe. The plunger has a generally tubular shape and isarranged with a number of recesses 78, where each recess is providedwith a conical surface 79, which conicity corresponds to the conicalpart 62 of the inner surface of the activator. The inner end of theplunger is arranged with two transversal protrusions 80 adapted to bearranged in the slots of the rear extension tube. A compression spring82, shown with broken lines in the FIGS. 6-9, is arranged in the plungerbetween the activator and an inner stop surface 84 of the plunger.

The auto-injector is designed to function as follows. When the injectoris loaded and ready to use, a syringe 24 is placed in the needle cover18. Preferably the syringe with its needle and the inner surface 34 ofthe needle cover are sterilised after assembly. Due to the sealed-offspace, because of the closed needle cover and the seal 30 between thesyringe and the needle cover, the syringe is kept sterile.

The compression spring 82 is in a compressed state in the plunger 76between its stop surface 84 and the end wall 86 of the activator. Theplunger is prevented from moving due to that the arms 58 withprojections 60 of the activator are abutting the inner surface of therear extension tube 46 and that the conical surfaces of the plunger andthe activator 62 and 78 are abutting each other.

In order to activate the injector, a two-step operation is needed, whichenhances the security against misfiring. Firstly the injector has to bepressed with its injection end, the right end in FIG. 2, against theinjection place, for example the leg of the patient. This causes theneedle cover 18 and the front extension tube 21 to move inside thehousing, FIG. 6, and thus the rear extension tube 46 since it isconnected to the front extension tube. The end of the rear extensiontube will come in contact with the conical surface 16 of the tubularpassage, whereby the end of the rear extension tube will flex outwardlydue to its slots 48. Because the arms 68 of the locking device rest onthe outer surface of the rear extension tube, due to the sidewardlyextending protrusions 72, the arms of the locking device also flexoutwardly.

This action enables the activator tube 54 to be pressed into thehousing, FIG. 7, and in relation to the rear extension tube, by afinger, whereby the outwardly directed protrusions 60 of the inner endof the activator are moved out of the rear extension tube. Because ofthe slots of the activator, the inner end will flex outwards and therebyrelease the plunger from its contact with the activator via the conicalsurfaces. The release of the plunger 76 will cause it to press againstthe plunger of the syringe due to the compression spring 82. Due to theincompressibility of the liquid of the syringe and the small diameter ofthe passage of the needle, the force from the plunger will cause thesyringe to move forward whereby the needle 26 will penetrate the endwall 20 of the needle cover and enter into the patient, FIG. 8. Theprotrusions 28 of the syringe will then abut the inner end 88 of thefront end piece, whereby the force from the plunger and the compressionspring will cause the plunger of the syringe to move, and thereby theliquid to be injected.

The forward movement of the plunger will cause its ribs 80 to come incontact with the snap fits 32 of the needle cover when the injectionmovement is almost completed. This causes the front and rear extensiontubes to be released from each other, whereby the front extension tube,and thus the needle cover because it is abutting the rear end of theneedle cover, are urged forward by the compression spring 74. When thepatient removes the injector, the compression spring pushes the needlecover out of the housing, thereby covering the needle, until its ledge36 abuts a shoulder 90 on the inner wall of the housing, FIG. 9. Thearms 42 of the lock ring have then been moved in position correspondingto the openings 11 of the housing and pushed into these by theelasticity of the arms. If one tries to push the needle cover in again,the protrusions 44 of the arms will prevent this by stopping against thesurfaces of the openings. The needle cover is further prevented frombeing pulled out from the front end piece, FIG. 2, because of a ledge 92on the outer surface of the needle cover and a ledge 94 on the innersurface of the front end piece.

FIG. 10 shows a variant of holding means for stopping and holding thesyringe when injecting the medicament instead of the protrusions 28 asdescribed above. In this case the front end of the syringe is arrangedwith a somewhat conical surface 100 and the inner surface of the frontportion of the needle cover 18 is arranged with a corresponding conicalsurface. When the syringe is moved forward after activation the conicalsurfaces meet and will retard the movement of the syringe. The syringeis now held in position when the plunger is pushed into the syringe. Theconical surfaces have two advantages that are useful for someapplications. Firstly the conical surfaces provide a softer stop of thesyringe thereby preventing, or at least greatly reducing, the risk ofbreakage of the syringe when it is stopped. Secondly, with thisarrangement the syringe is held at it's strongest point, which alsoprevents breakage. This also enables the ability to adjust spring forcesto fine tune the device to various friction forces when the syringe ismoved. It should be understood that the holding means may have manydifferent configurations in order to obtain the desired function. Forexample, resilient material may be arranged at the front portion of theneedle cover in order to catch and hold the syringe. It is also to beunderstood that the conical surfaces or the resilient material may bearranged in other parts of the device than the needle cover if thedevice is configured differently.

In a further variant of the present invention, for facilitating themanufacture of the auto-injector as regards sterilising the needle, itis conceivable to exclude a major portion of the end wall of the needlecover and to have a conventional needle cover of rubber or plasticpushed on the needle, in the way that sterilised syringes normally aredelivered after filling and sterilisation, where the needle cover of thesyringe preferably protrudes somewhat outside the needle cover of theauto-injector. Before use of the auto-injector, the user removes theneedle cover of the syringe, after which the auto-injector is used asdescribed above. With this variant, the needle may be sterilised beforeassembly in the auto-injector, which, in terms of manufacture, is asimpler step than sterilising the front part of the auto-injector andsyringe, that has to be done if the interior of needle cover of theauto-injector is used as a sterile environment.

With the present invention, it is also conceivable that, instead ofactivating the needle cover in order to extract it from theauto-injector body at the end of the injection cycle for covering theneedle afterwards, the syringe is pushed back into the auto-injectorbody at the end of the injection cycle by appropriate means.

Even though the auto-injector described is utilizing a syringe, it is tobe understood that other appropriate drug containers can be used, suchas cartridges, ampoules and the like.

It is also conceivable to arrange the auto-injector with some kind of“emergency situation” means. This type of means will disable the needfor performing said two-step operation. This may for example be done byhaving a member, such as a sliding button on the housing, by which therear extension tube may be pushed backwards whereby the end of the rearextension tube and the arms of the locking device will flex outwards,thereby releasing the activator tube. The member is preferably held inthis position after being placed there. The auto-injector can now beactivated by merely pushing the activator tube.

This may be useful when a patient has an acute need for medicament, suchas an acute allergic attack, and it might be too difficult or timeconsuming to remember the two-step operation as described above. In thiscase, a quick slide of the “emergency” button immediately sets theinjector ready for injection.

It is to be understood that the embodiments described above and shown onthe drawings are to be regarded as non-limiting examples of the presentinvention, and that it may be modified within the scope of protection asdefined by the patent claims.

1. Device for auto-injection of a dose of medicament, comprising: ahousing arranged to contain a medicament container therein andcomprising a needle cover with a contact part intended to be appliedagainst an injection site, spring means capable of, upon activation,pushing the needle past the end of the needle cover as well as operatingthe medicament container to supply the dose of medicament, first lockingmeans capable of locking the spring means in a pressurized state, firstactivating means capable of, upon manual operation, releasing the springmeans for injection, second locking means capable of locking the firstactivating means, second activating means comprising the needle cover,capable of releasing the second locking means when the contact part isexposed to pressure, wherein the first locking means is arranged anddesigned such that the second locking means is also capable of lockingthe first locking means for preventing the spring means from beingreleased when the device is operated in a sequence in which the firstactivating means is depressed, held depressed, and then the secondactivating means is exposed to pressure.
 2. Device according to claim 1,wherein the first locking means further is arranged and designed suchthat the second locking means is prevented from being released if thefirst activating means is operated at the same time as the secondactivating means is exposed to pressure.
 3. Device according to claim 1,wherein the needle cover surrounds a needle arranged to the medicamentcontainer and extends at least the length of the needle.
 4. Deviceaccording to claim 3, further comprising: second spring means capable ofpushing the needle cover over the needle after injection, third lockingmeans capable of locking the second spring means in a pressurized stateduring injection, and third activating means capable of releasing thesecond spring means upon end of injection.
 5. Device according to claim4, further comprising a fourth locking means capable of locking theneedle cover in a covering position after injection.
 6. Device accordingto claim 1, wherein the needle cover completely encloses a needle andthe needle is sterile.
 7. Device according to claim 1, furthercomprising holding means capable of retardation of the movement of themedicament container.